In lamps utilized for marking, signalling and the like in automotive vehicles, it is common to provide a housing and lens with some type of seal therebetween. Such applications include carriers of dusty, corrosive or flammable materials. In some instances, the seal is provided for the protection of the internal components of the lamp. In other applications, such as fuel tankers, the seal is utilized to prevent flammable or explosive vapors from reaching the electrical contacts of the lamp.
Heretofore, the most common construction comprised a housing and a lens having telescoping portions with a resilient seal interposed therebetween. In some types, the lens is retained in position by the interrelationship of the components. Typical of such a construction are the lamps described in U.S. Pat. Nos. 3,244,869, 3,096,026 and 2,707,747.
These earlier devices shared one common failure point, and this was the sealing area. Due to the variations in thermal expansion between a plastic lens, a rubber sealing ring and a metal housing, the assembly tended to loosen in elevated temperature service, and to "lock-up" in low temperature service. In sub-zero temperatures, such lamps were virtually impossible to service and required that the lens be broken for a simple change of bulb.
Consequently, the objects of this invention comprise the provision for a lamp which may be readily serviced, without tools, at both elevated and sub-zero temperatures. Further, it is an object of this invention to provide a lens/housing engagement which is not adversely affected by climatic conditions. Still further, it is an object to provide a lens, housing and interposed seal providing a satisfactory locking means without the necessity of extremely close tolerances.
Further objects include the provision for a lamp utilizing a low-cost molded seal, which may be easily manufactured, assembled and serviced as required.